Blade mounting structure of lawn mower

Abstract

A blade mounting structure of a lawn mower includes a blade holder including a shaft-mounted section connected to an output shaft of an engine, and a blade mounting section having a grass cutting blade mounted thereto. The blade holder further includes a connecting leg section located between the shaft-mounted section and the blade mounting section and interconnecting the shaft-mounted section and the blade mounting section. The connecting leg section has a wall thickness dimension gradually decreasing in a direction from the shaft-mounted section toward the blade mounting section.

What is claimed is: 
     
       1. A blade mounting structure of a lawn mower, which comprises
 a blade holder including a shaft-mounted section connected to an output shaft of a power source, and a blade mounting section having a grass cutting blade mounted thereto, 
 the blade holder further including a connecting leg section located between the shaft-mounted section and the blade mounting section, interconnecting the shaft-mounted section and the blade mounting section, and functioning as an impact absorbing member, 
 wherein the blade mounting section is provided on an extended axial line of the output shaft and is mounted to a center part of the grass cutting blade, and 
 wherein the connecting leg section comprises a plurality of stay leg portions disposed about the shaft, and an outer interval between outer surfaces of opposed stay leg portions of the plurality of stay leg portions and an inner interval between inner surfaces of the opposed stay leg portions of the plurality of stay leg portions gradually increase in the direction from the shaft-mounted section toward the blade mounting section, and a wall thickness dimension of each of the plurality of stay leg portions gradually decreases in the direction from the shaft-mounted section toward the blade mounting section, 
 wherein the connecting leg section is configured to absorb a bending moment and a twisting moment resulting from an impact load which is input to a blade mounting section side portion of the connecting leg section by way of the grass cutting blade and the blade mounting section, 
 wherein a yield point of the connecting leg section to the bending moment and the twisting moment is substantially uniform throughout an entire region from a shaft-mounted section side portion of the connecting leg section to the blade mounting section side portion of the connecting leg section, and 
 wherein the connecting leg section is deformable to absorb the bending moment and the twisting moment resulting from the impact load prior to the shaft-mounted section and the blade mounting section. 
 
     
     
       2. The blade mounting structure according to  claim 1 , wherein the shaft-mounted section includes a cylindrical opening where the output shaft is inserted. 
     
     
       3. The blade mounting structure according to  claim 1 , wherein the plurality of stay leg portion are all connected to the blade mounting section, which is a single continuous member. 
     
     
       4. The blade mounting structure according to  claim 1 , wherein a rotation axis of the grass cutting blade is positioned at a center of the grass cutting blade. 
     
     
       5. The blade mounting structure according to  claim 1 , wherein a rotation axis of the grass cutting blade is positioned at a through hole. 
     
     
       6. A blade mounting structure of a lawn mower, which comprises
 a blade holder including a shaft-mounted section connected to an output shaft of a power source, and a blade mounting section having a grass cutting blade mounted thereto, 
 the blade holder further including a connecting leg section located between the shaft-mounted section and the blade mounting section, interconnecting the shaft-mounted section and the blade mounting section, and functioning as an impact absorbing member, 
 wherein the blade mounting section is provided on an extended axial line of the output shaft and is mounted to a center part of the grass cutting blade, 
 wherein the connecting leg section is a cylindrical member having an axis coaxial with the output shaft, and the cylindrical member has an outer diameter and an inner diameter gradually increasing in the direction from the shaft-mounted section toward the blade mounting section, and a wall thickness dimension of the cylindrical member gradually decreases in a direction from the shaft-mounted section toward the blade mounting section, 
 wherein the connecting leg section is configured to absorb a bending moment and a twisting moment resulting from an impact load which is input to a blade mounting section side portion of the connecting leg section by way of the grass cutting blade and the blade mounting section, 
 wherein a yield point of the connecting leg section to the bending moment and the twisting moment is substantially uniform throughout an entire region from a shaft-mounted section side portion to the blade mounting section side portion of the connecting leg section, and 
 wherein the connecting leg section is deformable to absorb the bending moment and the twisting moment resulting from the impact load prior to the shaft-mounted section and the blade mounting section.